A Biometry Core is proposed as a resource that will be available to investigators of all Center projects and to other investigators who contribute to the research base, both BIOMED and EEHSR, pursuing projects related to arthritis and musculoskeletal conditions. The principal functions of this core are; 1) to assist investigators ina the design, conduct, analysis, and reporting of their studies; 2) to maintain national registry and clinical databanks needed as special resources for investigators both internal and external to the Center; 3) train investigators, graduate students, and other staff in the proper methods of study design, conduct, analysis, and reporting of studies; 4) manage the tissue repository. Edward H. Giannini, MSc, DrPH, is the proposed Director of this core, and Shumei Guo, PhD, will serve as the senior biostatistician. The operation of the Exploratory Research Center for Juvenile Rheumatic Diseases, which began in September of 1993, as well as numerous external collaborations, has allowed Dr. Giannini to develop and mature the Biometry core during the last 2 years. The tissue repository, which presently contains 1377 tissues, is an important special resource located within this core. Robert A. Colbert, MD, PhD, is the proposed manager of the repository. During the operation of this project, the repository will log aliquot tissues including serum, DNA,a nd synovium from children with pediatric rheumatic disease. Investigators, both from within the Center and external to it, will have access to this important resource. Specifically, tissue repository personnel will: 1) collect and store samples from well characterized patients with pediatric rheumatic illness; 2) provide and maintain a log and monitor the use of these samples; 3) continuously replenish samples as required to maintain the viability of the repository.